1. Technical Field
The present invention relates to optical scanners and image forming apparatuses.
2. Related Art
For example, as an optical scanner for performing drawing by optical scanning in a laser printer or the like, an optical scanner which is formed of a torsion oscillator and uses an actuator has been known (see, for example, JP-A-2005-181395 (Patent Document 1)).
In Patent Document 1, an actuator having an insulating substrate in which a pair of permanent magnets is provided and a scanner main body supported by the insulating substrate so as to be located between the pair of permanent magnets is disclosed. Moreover, the scanner main body has a frame-shaped supporting section, a frame-shaped outside movable plate provided inside the supporting section, and an inside movable plate (mirror) provided inside the outside movable plate. Furthermore, the outside movable plate is connected to a supporting section via a pair of first torsion bars extending in an X-axis direction, and the inside movable plate is connected to the outside movable plate via a second torsion bar extending in a Y-axis direction perpendicular to the X-axis direction. Moreover, the outside movable plate and the inside movable plate each have a coil.
In the actuator structured as described above, by the action of the magnetic fields generated from the coils and the magnetic field generated between the pair of permanent magnets by energization, the outside movable plate turns with the inside movable plate about an X axis using the first torsion bar as a central axis, and the inside movable plate turns about a Y axis by using the second torsion bar as a central axis.
As described above, in the actuator of Patent Document 1, the mechanism which turns the inside movable plate about the X axis and the mechanism which turns the inside movable plate about the Y axis differ from each other. This makes it impossible to turn the inside movable plate about the X axis and the Y axis under the same conditions. In addition, in the actuator of Patent Document 1, the magnetic field generated from the coil provided in the outside movable plate and the magnetic field generated from the coil provided in the inside movable plate interfere with each other, making it impossible to turn the inside movable plate about the X axis and the Y axis independently. Thus, the actuator of Patent Document 1 has a problem that it is impossible to turn the inside movable plate about the X axis and the Y axis with stability.